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Frozen Terminations

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TroyB21
TroyB21 Member Posts: 3
in THE MAIN WALL
I have a townhouse development that has been experiencing iced exhaust terminations forcing furnaces to shut off. They are a 90% Goodman, and were just installed 2 years ago. We have had issues from the very first winter, and have had no help from the mfg in dealing with this. My maintenance team has had to disconnect lines and blow hot air until the ice plugs have literally shot out of the 2" pvc. but this is only a temporary solution, until it freezes up again. Has anyone had any luck with changing the heating speed (or any other ideas) to prevent this from happening. BTW; this is happening at roof top terminations as well as side wall (short run/end unit apartments).

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  • SuperTech
    SuperTech Member Posts: 2,172
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    Are these concentric vents? What equipment are these vents from?
  • TroyB21
    TroyB21 Member Posts: 3
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    they are not concentric vents, both the intake and exhaust are separate 2" pvc. We are getting ice built up on the exhaust termination, even though the run length, amount of 90's etc. are within the installation specs. We just seem to have flue gasses that aren't warm enough to make it to atmosphere before freezing and building up at the end of the pipe.
  • pecmsg
    pecmsg Member Posts: 4,870
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    The runs are within install specs what about the termination points. Height, distance between Short or Long radius ells, T's
  • Jamie Hall
    Jamie Hall Member Posts: 23,365
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    Where is this located? You may find that either you have to run the units hotter -- higher return temps -- to get the exhaust hotter, or you may find that you have to insulate the portions of the exhaust which are exposed to outside air -- inch and a half fiberglass. Or both.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • TroyB21
    TroyB21 Member Posts: 3
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    Where is this located? You may find that either you have to run the units hotter -- higher return temps -- to get the exhaust hotter, or you may find that you have to insulate the portions of the exhaust which are exposed to outside air -- inch and a half fiberglass.

    I am not sure how to adjust the return temps, but I like the idea and will look into further insulation in the attic, and maybe even on the exposed section of pipe at the roof. Thanks!
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
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    Insulation on pipe in cold spaces sounds right

    If it's still icing at outside end Maybe metal pipe at end instead with electric ice melt cable on outside , might have to insulate it too. Have to check out what temperature electric cable can take.
    TroyB21
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,567
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    If the exhaust is run through a cold area insulating the exhaust may be an option.

    Other than that have a tech check the furnace temperature rise it must be within the MFG limits but you may be able to lower the fan speed which will raise discharge temp and raise the exhaust temp.

    I would also limit the exposed pipe outside if possible.

    And if the MFG permits and only if they permit it a reducer on the exhaust would increase the outlet velocity which may help
  • DZoro
    DZoro Member Posts: 1,048
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    Both pipes must be insulated in attic or any other cold space. Make sure the termination is done properly above the roof. Exhaust straight up, no elbows. Intake 2-90* facing down and at least 12-18" away from exhaust. The exhaust must be higher than the intake. Slope toward the furnace minimum of 1/4" per foot when on a horizontal run.
    D
    Zman
  • Total1
    Total1 Member Posts: 44
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    Are the exhaust piping sloped back to the furnace ? This works well here even with -46 F .
    DZoroZman
  • mikeg2015
    mikeg2015 Member Posts: 1,194
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    I bet these units short cycle even in cold weather. I bet they are 45 or even 60k units on 20-30k heat loss. Short cycles never get the pipe hot enough to melt ice formed after the end of the last cycle.

    Best bet is insulation as mentioned. Even the unexposed sections. You need to get the exhaust hot to melt the ice.

    Could also change the thermostats to one that has adjustable cycles per hour and use a setting of 2 CPH. White ROdgers also have thermostats with adjustable differentials. The goal is longer run times.

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